The research project is directed toward the understanding of the nature of the cell membrane receptor which serves as the so-called "sugar carrier" in the process of glucose penetration into cells. Phlorizin and a number of organically synthesized analogs are preferentially bound to this glucose transport process. This characteristic binding property serves as a "fingerprint" which is being used to identify the membrane component in attempts to isolate it from various cell membranes.Radioactively labelled phlorizin and phlorizin analogs have been prepared to serve as easily measurable marker molecules in these investigations. It is anticipated that the proposed work will yield valuable information about the mechanism by which sugars penetrate cell membranes. A study of the processes by which a basic phenomenon is inhibited has historically often led to an understanding of the phenomenon itself. Similarly, an understanding of the basic mechanism by which sugars penetrate cell membranes is a prerequisite for the eventual interpretation of disease conditions in which the process is abnormal, as for example in diabetes mellitus, malabsorption syndromes, etc.